Method for recovering hydrocarbons from tar sands and oil shales

ABSTRACT

A method for treating hydrocarbonaceous deposits to recover a petroleum-like hydrocarbon portion and a cleaned particulate substrate portion. Hydrocarbonaceous ore containing bitumen and/or kerogen is crushed or otherwise comminuted to the particle size of sand or smaller. The comminuted ore is mixed with water to form a slurry, is heated to between 60° C. and 100° C., and is blended with an oxidant in aqueous solution, preferably hydrogen peroxide. Both free interstitial hydrocarbons and those hydrocarbons bound electrostatically to the surfaces of clay-like particles in the ore are released from the rock substrate in a putative electrophysical reaction in the presence of the oxidant. Some of the released bituminous and kerogenic compounds are then controllably cleaved by the oxidant in a limited Fenton&#39;s reaction to yield organic compounds having lower average molecular weights which are suitable for refining as oil after separation from the process water phase and the residual rock substrate. The water and rock tailings from the process are substantially free of hydrocarbon contamination and are environmentally suitable for landfill disposal.

[0001] The present application is a Continuation of myContinuation-In-Part allowed application Ser. No. 09/451,293 filed Nov.30, 1999 which is a Continuation-In-Part of my application Ser. No.09/304,377 filed May 4, 1999, now matured as U.S. Pat. No. 6,096,227which is a Continuation-In-Part of my application, Ser. No. 08/971,514filed Nov. 17, 1997, now matured as U.S. Pat. No. 5,928,522 issued Jul.27, 1999, which is a Continuation-In-Part of my application, Ser. No.08/807,643 filed Feb. 27, 1997, now matured as U.S. Pat. No. 5,797,701issued Aug. 25, 1998.

DESCRIPTION

[0002] The present invention relates to methods for recoveringpetroleum-like hydrocarbons from hydrocarbon-containing geologicalreservoirs, and more particularly to a method for processinghydrocarbon-containing geologic material, including tar sands, oilsands, oil sandstones, and oil shales, to recover petroleum-likehydrocarbons, and especially crude oil, therefrom and to render the rocksubstrate residues suitable for environmentally-acceptable disposal.

[0003] As used herein, hydrocarbonaceous deposit is to be taken toinclude tar sands, oil sands, oil sandstones, oil shales, and all othernaturally-occurring geologic materials having hydrocarbons containedwithin a generally porous rock-like inorganic matrix.

[0004] Tar sands are naturally-occurring geological formations found in,for example, Canada (Alberta). Such sands have potential for yieldinglarge amounts of petroleum. Tar sands are porous sands generallycontaining substantial amounts of clay and filled with heavy, relativelysolid asphaltic hydrocarbons. Most of these tar-like bituminousmaterials are residues remaining in reservoir rocks after lighter (lowermolecular weight) crude oils have escaped. The largest of the world'star sand deposits occur in northern Alberta along the Athabaska River.Tar sand layers in this area may be more than 60 meters thick and lienear the surface over a total area of about 50,000 km². They areestimated to contain a potential yield in excess of 1.6 trillion barrelsof oil.

[0005] Oil shales are related to oil sands and tar sands; however, thesubstrate is a fine-grained laminated sedimentary rock containing anoil-yielding class of organic compounds known as kerogen. Oil shaleoccurs in many places around the world. Particularly kerogen-rich shalesoccur in the United States, in Wyoming, Colorado, and Utah, and areestimated to contain in excess of 540 billion potential barrels of oil.

[0006] In the known art of petroleum recovery from hydrocarbonaceousdeposits, the high molecular weight asphaltic or kerogenic material maybe driven out of the sands, sandstones, or shales with heat. Forexample, in a known process for recovering kerogen from oil shale,crushed shale is heated to about 480° C. to distill off the kerogenwhich is then hydrogenated to yield a substance closely resembling crudeoil. Such a process is highly energy intensive, requiring a portion ofthe process output to be used for firing the retort, and thus isrelatively inefficient. Also, a significant percentage of the kerogenmay not be recovered, leaving the process tailings undesirable forlandfill.

[0007] Other known processes, for recovering bitumen from tar sands forexample, may require the use of caustic hot water or steam. For example,a process currently in use in Canada requires that a hot aqueous slurryof tar sand be mixed with high concentrations of aqueous caustic soda tofractionate the bitumen into lower molecular weight hydrocarbons whichmay then be separated from the inorganic rock residues and refinedfurther like crude oil.

[0008] This process has several serious shortcomings. First, it isrelatively inefficient, recovering less than about 70% of thehydrocarbons contained in the sands. “Free” hydrocarbons, that is,compounds mechanically or physically contained interstitially in therock, may be recovered by this process; but “bound” hydrocarbons, thatis, compounds electrostatically bound by non-valence charges to thesurface of clays or other fines having high electronegative surfaceenergy, are not readily released by the prior art process. In fact, highlevels of caustic may actually act to inhibit the desired release oforganic compounds from such surfaces. Thus, the prior art process iswasteful in failing to recover a substantial portion of the hydrocarbonpotential, and the substrate residue of the process may containsubstantial residual hydrocarbon, making it environmentally unacceptablefor landfill.

[0009] Second, both the aqueous residual and the sand/clay residue arehighly caustic and may not be spread on the land or impounded in lagoonswithout extensive and expensive neutralization.

[0010] Third, the caustic aqueous residual may contain high levels ofdissolved petroleum, which is non-recoverable and also toxic inlandfill. Such residual also has a high Chemical Oxygen Demand (COD),making such residual substantially anoxic and incapable of supportingplant or animal life.

[0011] Fourth, oils recovered by the prior art process typically havehigh levels of entrained or suspended fine particulates which must beseparated as by gravitational settling, filtration, or centrifugationbefore the oils may be presented for refining.

[0012] Fifth, because of relatively long settling times required forseparation of solid particulates from the aqueous medium and therecoverable hydrocarbons, which typical are highly and stably emulsifiedas a colloidal suspension, the prior art process is not generallyamendable to a continuous-feed operation.

[0013] Sixth, the present-day cost of oil recovered from Albertan tarsands by a prior art process requires a substantial governmental subsidyto match the world spot price of crude oil.

[0014] It is a principal object of the invention to provide an improvedprocess for recovering hydrocarbons from hydrocarbonaceous deposits ingreater than 90% yield.

[0015] It is a further object of the invention to provide an improvedprocess for recovering hydrocarbons from hydrocarbonaceous deposits ingreater than 99% yield.

[0016] It is a still further object of the invention to provide animproved recovery process which provides a substrate residue which isacceptable under applicable guidelines for landfill disposal.

[0017] It is a still further object of the invention to provide animproved recovery process which can recover both free and boundhydrocarbon compounds from geologic substrates and thereby recover ahigh percentage of all of the hydrocarbons therein.

[0018] It is a still further object of the invention to provide animproved recovery process which is substantially less expensive tooperate on a per-unit of ore basis than are known treatment processes.

[0019] It is a still further object of the invention to provide animproved recovery process which can yield oil at a unit cost competitivewith that of well-produced crude oil.

[0020] Briefly described, hydrocarbonaceous ore containing bitumenand/or kerogen is crushed or otherwise comminuted to the consistency ofsand. The comminuted ore is mixed with water to form a slurry, is heatedto between about 60° C. and about 100° C., and is blended with anoxidant in aqueous solution, preferably hydrogen peroxide. Both freeinterstitial hydrocarbons and those hydrocarbons bound electrostaticallyto the surfaces of clay-like particles are released from the rocksubstrate, possibly by an electrophysical reaction in the presence ofthe oxidant. A portion of the released bituminous and kerogeniccompounds are then cleaved by the oxidant in a controlled Fenton'sreaction to yield organic compounds having lower molecular weights whichare suitable for refining as oil after separation from the process waterphase and the residual rock substrate. The water and rock tailings fromthe process are substantially free of hydrocarbon contamination and areenvironmentally suitable for disposal.

[0021] The foregoing and other objects, features, and advantages of theinvention, as well as presently preferred embodiments thereof, willbecome more apparent from a reading of the following description inconnection with the accompanying drawing, in which FIG. 1 is a schematicflowpath of a semi-continuous process for recovering hydrocarbons fromhydrocarbonaceous ores in accordance with the invention. Since orevolumes to be treated can be relatively large, it may be preferable toconfigure the process for continuous throughput, althoughsemi-continuous (as shown in FIG. 1) and batch systems are within thescope of the invention and all such processes may be configured ofconventional apparatus without undue experimentation or furtherinvention.

[0022] I have found that my oxidative stripping processes, forremediation of hydrocarbon-contaminated soils as disclosed in my U.S.Pat. No. 5,797,701, and for treatment of oil refinery wastes asdisclosed in my U.S. Pat. No. 5,928,522, and for treatment of industrialsludges as disclosed in my U.S. patent application, Ser. No. 09/304,377filed May 4, 1999, are readily adaptable as described herein to thetreatment of hydrocarbonaceous geologic deposits such as tar sands, oilsands, oil sandstones, oil shales, and the like, to recover a highpercentage of the hydrocarbon content therefrom. The relevantdisclosures of U.S. Pat. Nos. 5,797,701 and 5,928,522 are herebyincorporated by reference.

[0023] Referring to FIG. 1, in a hydrocarbon recovery process embodyingthe invention, hydrocarbonaceous ore 10, which has been mined, crushed,ground, screened, or otherwise pre-treated to eliminate large rocks anddebris and to yield a feedstock having particles preferably less thanabout 2 mm in diameter (sand size), is mixed with water in a slurryhopper 11 to form a pumpable slurry 12 having a weight percentproportion of ore to water of between about 2:1 and about 1:1. Theslurry is conditioned by agitation and heating to a temperature betweenabout 50° C. and about 80° C. to release free hydrocarbons, melt waxyhydrocarbon solids, reduce the viscosity of the batch, reduce thedensity of hydrocarbon fractions within the batch, and begin to breaksurface adhesion of hydrocarbon compounds bound to substrate surfaces.The free hydrocarbons thus released define a first hydrocarbon residue.

[0024] In a reactor vessel 14, slurry 12 is heated to a temperaturebetween about 60° C. and about 100° C. and is blended with an aqueoussolution 16 containing an oxidizing reagent to produce a slurry having alevel of oxidant equivalent to a hydrogen peroxide percentage betweenabout 0.1% and about 10.0% in the water phase by weight. Various wellknown oxidants, for example, potassium permanganate and sodium peroxide,can perform the oxidative function of the subject process, but hydrogenperoxide is the preferred oxidant because it ultimately decomposes towater and oxygen, leaving no elemental or mineral residue in thetailings.

[0025] In the presence of a hot oxidant, the electrostatically boundhydrocarbons are released from the surface of substrate particles,especially very fine clay or clay-like particles, the bound hydrocarbonsthus released defining a second hydrocarbon residue.

[0026] Although the accuracy of a theory is not relied upon forpatentability of the methods disclosed and claimed herein, it iscurrently believed by the inventor that the hydrocarbon moleculesadhered to the rock substrate particles in the ore carry positivenon-valence charges which bind them to negative surface charges on theparticles, especially on clay-sized fines; and further, that the hotoxidant, in a mechanism not yet fully understood, tends to neutralizethe non-valence charges on either or both of the hydrocarbon moleculesand the particle surfaces, thereby releasing one from the other.

[0027] The hot oxidant functions further in a second way to oxidizeallyl and other hydrocarbon moieties to lighter petroleum fractions viathe well-known Fenton's reaction. Hydrogen peroxide reacts withubiquitous ferrous ions to produce an hydroxyl radical in an acidifiedaqueous medium.

H₂O₂+Fe⁺²-->ÿOH+OH—+Fe⁺³   (Eq. 1)

[0028] The resultant hydroxyl free radicals (OH) are extremely powerfuloxidizers that progressively react with organic compounds through aseries of oxidation reactions. During the process, the oxidationreactions proceed by degrading the organic constituents (b) having longchain lengths (n carbon atoms) into a greater number of molecules (b+c)having less complex and shorter carbon chain lengths (n−á):

H₂O₂+bC_(n)H_(n)-->H₂O+(b+c)C_(n−á)H_(n)   (Eq. 2)

[0029] In an excess of oxidant, all organic carbon may be converted toCO₂ in accordance with Eq. 3 (not balanced):

H₂O₂+C_(n)H_(n)>H₂O+nCO₂   (Eq. 3)

[0030] However, in a process in accordance with the invention, whereinreaction time, temperature, and the amount of oxidant are controlled bya programmable controller 17, Fenton's reaction is limited to breakingrelatively few covalent bonds, sufficient only to reduce the averagemolecular weight of the bituminous or kerogenic hydrocarbons in thefirst and second residues to approximately that of conventional crudeoil produced from a well.

[0031] As the slurry is heated and agitated, the larger sand-sizedparticles, substantially freed of hydrocarbons, settle out of theslurry, and a froth 18 rich in first and second hydrocarbon residuesrises to the surface as the aqueous and organic phases separategravitationally. Froth 18 typically contains substantial amounts ofentrained water and substrate fines. The first aqueous phase tailings20, containing the clean sand substrate, may be drawn off from thebottom of the reaction vessel 14 and landfilled directly as desired. Forprocess efficiency, froth 18 may be transferred to a second reactor 22,as shown in FIG. 1, permitting generation of the next batch in vessel 14while froth 18 is being further processed (semi-continuous, or movingbatch, process); or, all steps requiring a vessel may be carried out ina single reactor.

[0032] To remove water and fines from the organic phase, the frothcontaining oxidized and non-oxidized bitumen and/or kerogen is mixed,preferably at a ratio of 1:1, with a so-called “cutter stock” 24,typically either diesel oil or naphtha, to dilute and solubilize thebitumen or kerogen, causing a further separation of the froth into asecond aqueous phase containing the fines and an organic phasecontaining the hydrocarbons. In some operations, this separation may beeffected by discharging the blended froth 26 through a commercialcentrifuge 28, from which the aqueous phase tailings 30 may belandfilled directly. Typically, the hydrocarbon content of the combinedfirst and second tailings is less than about 1%, which meets therequirements for disposal in accordance with US government regulations.

[0033] The organic phase 32 may be subjected to distillation 34 toremove and recover for recycling the cutter stock 24. Thepartially-oxidized bitumen and/or kerogen 36, recovered from ore 10 bythe subject process and free of the residual water and fine particulateswhich characterize hydrocarbon residues produced by the known artprocess, now may be sent for further processing such as to an oilrefinery.

[0034] In practical applications of the subject process to recovery ofbituminous liquids from Athabaska tar sands, material approximatingcrude oil is recoverable at a lower cost per barrel than the world spotprice for crude oil.

[0035] From the foregoing description it will be apparent that there hasbeen provided an improved method for economically recoveringpetroleum-like hydrocarbon residues from hydrocarbonaceous geologicaldeposits and for discharging a substrate residue environmentallysuitable for landfill disposal. Variations and modifications of theherein described method, in accordance with the invention, willundoubtedly suggest themselves to those skilled in this art.Accordingly, the foregoing description should be taken as illustrativeand not in a limiting sense.

What is claimed is:
 1. A method for treating an aqueous slurry of hydrocarbonaceous ore containing hydrocarbon compounds and substrate solids to recover hydrocarbon residues therefrom, comprising the steps of: a) conditioning said slurry by heating to mobilize a first portion of said hydrocarbon residues; b) adding an amount of an oxidant to said slurry; c) liberating a second portion of said hydrocarbon residues from said substrate solids contained in said slurry; d) oxidizing at least part of said first and second hydrocarbon residue portions; and e) separating a liquid effluent containing said hydrocarbon residues from said substrate solids.
 2. A method in accordance with claim 1 wherein said slurry is heated to a temperature between about 60° C. and about 100° C.
 3. A method in accordance with claim 1 wherein said oxidant is selected from the group consisting of hydrogen peroxide, sodium peroxide, and potassium permanganate.
 4. A method in accordance with claim 1 wherein said oxidant is present in said slurry after said adding step in an amount between about 0.1 weight percent and about 10.0 weight percent relative to the weight of water in said slurry.
 5. A method in accordance with claim 1 further comprising the step of adjusting the weight ratio of water to ore in said slurry to between about 1:1 and about 2:1 prior to said conditioning step.
 6. A method in accordance with claim 1 wherein said liquid effluent contains water.
 7. A method in accordance with claim 1 wherein said ore is selected from the group consisting of tars, tar sands, oil sands, oil shales, and oil sandstones.
 8. A method in accordance with claim 7 wherein said ore includes clay-size particles.
 9. A method in accordance with claim 8 wherein at least a part of said second portion of hydrocarbon residues is liberated from said clay-size particles.
 10. A method in accordance with claim 1 wherein said method is carried out in a process selected from the group consisting of continuous, semi-continuous, batch, and combinations thereof.
 11. A method in accordance with claim 1 wherein all of said steps are carried out in one vessel.
 12. A method in accordance with claim 1 further comprising the steps of: a) mixing said liquid effluent with a cutter stock to dilute and solubilize said first and second hydrocarbon residue portions; and b) b) separating said diluted and solubilized residue portions from said substrate solids.
 13. A method for treating an aqueous slurry of ore containing hydrocarbon residues and substrate solids to recover hydrocarbons therefrom, comprising the steps of: a) conditioning said slurry by heating to a temperature between about 60° C. and about 100° C. to mobilize first hydrocarbon residues; b) adding an amount of an oxidant to said slurry; d) liberating second hydrocarbon residues from said substrate solids contained in said slurry; e) oxidizing a portion of said first and second hydrocarbon residues; f) separating a liquid effluent containing said first and second hydrocarbon residues and a first portion of said substrate solids from a second portion of said substrate solids; and g) separating said first and second hydrocarbon residues from said first portion of said substrate solids.
 14. A method in accordance with claim 13 wherein said oxidant is hydrogen peroxide.
 15. A method in accordance with claim 13 wherein at least one of said first and second hydrocarbon residues includes hydrocarbons selected from the group consisting of bitumen and kerogen.
 16. A method in accordance with claim 13 wherein said first portion of said substrate solids includes clay-like particles.
 17. A method in accordance with claim 13 wherein said step of separating said first and second hydrocarbon residues from said first portion of said substrate solids further comprises the steps of: a) mixing said liquid effluent with a cutter stock to dilute and solubilize said first and second hydrocarbon residues; and b) separating said diluted and solubilized residues from said substrate solids.
 18. A method in accordance with claim 17 further comprising the step of separating said cutter stock from said hydrocarbon residues to yield said hydrocarbons. 